As is known, manufacturing techniques for semiconductor devices have been successfully exploited also outside the field closely related to microelectronics and for instance they have been used to develop microelectromechanical and microfluidic systems for a number of applications.
The field of fluidics, in particular, has benefited from the possibility of manufacturing miniaturized components, such as micropumps and valves, which allow volumes of liquids in the order of microlitres or smaller to be processed with a very high degree of precision. Thus, devices for ink-jet printing, biomedical devices (for example, insulin pumps), and devices for biochemical analyses (for example, microreactors for amplification and detection of nucleic acids), among others, have been improved.
However, the basic components and microfluidic devices available (micropumps and valves) are still relatively complex and their structure is a limitation to miniaturization, besides entailing non-negligible manufacturing costs. For example, micropumps and valves must be equipped with movable members and electromechanical actuators which, by acting on the movable members, control the movement of the fluids in accordance with the required functions. Generally, the integration of the actuators is rather difficult and complicates the manufacturing processes. In fact, the actuators normally require dedicated structures, which must often be made from specially designated structural layers. Furthermore, the actuators employ special materials, such as piezoelectric or magnetic materials, which require changes to the most common manufacturing processes and additional processing steps (for example, deposition, masking, and photolithographic definition of layers of special materials).
It must also be considered that in many cases the tightness of the valves, especially when integrated into membrane micropumps, is not optimal and can be the cause of leakage and backflow, which affect the working of the device.